Nonalcoholic fatty liver disease (NAFLD) is a common liver disease and a major cause of related complications such as cirrhosis and hepatocellular carcinoma (HCC). NAFLD progresses through the stages of simple steatosis, nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and HCC. However, NAFLD usually cannot be diagnosed in a timely manner, which is largely attributed to the asymptomatic features of NAFLD patients and the lack of an effective and accurate noninvasive screening approach. Although liver biopsy has been recognized as a gold standard for diagnosing NAFLD, this approach is not suitable for screening and monitoring NAFLD because of its high cost and invasiveness. Several noninvasive screening and diagnostic systemic assessments have been developed in recent years for NAFLD evaluation. Here we summarize the current status and methods for NAFLD diagnosis, including both noninvasive (imaging, biomarkers) and invasive (liver biopsy) assessments. We further discuss the advantages and disadvantages of these developed diagnostic approaches for NAFLD.